Characteristics of La-Ca-Mn-O Tunneling MagnetoresistanceDevices and Bi2Te3/LCMO Heterogeneous Junctions

• Main Authors: Li-Siang Guo, 郭禮翔
• Other Authors: Li-Min Wang
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/njsw38

碩士 === 國立臺灣大學 === 應用物理研究所 === 106 === This thesis studies the tunneling magnetoresistance / superconducting hybrid sensing components. The main structure is the growth of yttrium copper oxide (YBa2Cu3O7-δ) / barium titanate (SrTiO3) / barium calcium manganese oxide (La0.67Ca0.33MnO3) on a bi-crystal substrate. We use RF magnetron sputtering to deposit LCMO on the bi-crystal substrate, and then make the tunneling component and then use the laser pulse evaporation (PLD) to grow STO as the insulating layer to isolate the upper and lower superconducting layer and the insulating layer, and then YBCO is also plated by laser pulse evaporation. We use the yoke design below the superconducting phase transition temperature, and the reluctance ring has a larger reluctance, from 22% to 27.5%. We designed two different magnetoresistive elements, a YBCO film, and a new Washer-type graphic design. The LCMO film has a phase transition temperature of 240 K and a YBCO superconducting phase transition temperature of 86 K. It has a good phase transition temperature. We compare the presence or absence of superconducting rings and samples with or without twins because the defects on the twins did not show good tunneling reluctance properties in repeated experiments. The other part is to explore the characteristics of Bi2Te3 / LCMO bilayer membrane heterostructure. We first use the RF magnetron sputtering system to first coat the lower layer with LCMO film and then vacuum-evaporate the Bi2Te3 film to explore the characteristics of the heterostructure. Bi2Te3 film by Hikami-Larkin-Nagaoka (HLN) formula ∆σ_xx=(αe^2)/(2π^2 ℏ)[Ψ(1/2+ℏ/(4el_φ^2 B))-ln(ℏ/(4el_φ^2 B))] do the fitting to get α=1. It shows that the spin-orbit interaction force and magnetic scattering are very weak, and the energy gap of the heterostructure is about 0.50 eV, mainly from the contribution of LCMO. Calculate the energy barrier height at sample 1 V_bi=5.48 eV, and the potential barrier width t=2.07 nm. The energy barrier height at sample 2 is V_bi=5.52 eV, and the potential barrier width is t = 2.08 nm. The maximum reluctance of the heterojunction is 4.5%.